Medically reviewed by Saurabh Sethi, MD, MPH
Written by Jamie Eske
Auto-brewery syndrome, or gut fermentation syndrome, is a rare condition in which fungi in the gut rapidly convert carbohydrates into alcohol.
In recent years, news outlets have covered stories of people claiming that they have auto-brewery syndrome, but researchers are still uncovering its causes.
In this article, we discuss what auto-brewery syndrome is, what causes it, and the possible treatments. We also cover a few famous cases.
What is it?
Auto-brewery syndrome is a rare, potentially underdiagnosed condition that occurs when an overgrowth of certain types of fungus in the gut convert carbohydrates into alcohol.
Numerous microorganisms live in the gastrointestinal tract. Bacteria make up the vast majority of these organisms, with fungi accounting for less than 0.1% of the microbes inside the average human gut.
Candida, a type of yeast, is the most common fungal species in the gut.
Although low concentrations of fungus rarely cause problems, fungal overgrowth can have a significant effect on a person’s health and overall quality of life.
Yeasts and other fungi feed on the sugars and starches in food, which they convert into energy. This process also creates waste in the form of carbon dioxide and ethanol — a type of alcohol.
The ethanol that fungal fermentation produces will enter the bloodstream and travel throughout the body.
People who have auto-brewery syndrome may have high blood alcohol levels after ingesting a small quantity of alcohol or even no alcohol at all.
Auto-brewery syndrome can also cause the same physical and psychological symptoms that occur when a person is intoxicated or hungover.
Auto-brewery syndrome occurs as a result of an underlying condition, such as gastrointestinal disease and microbiome imbalances.
Certain medical conditions and factors can increase a person’s chances of developing auto-brewery syndrome.
- Crohn’s disease
- irritable bowel syndrome (IBS)
- small intestinal bacterial overgrowth
- short bowel syndrome
- a weakened immune system
Frequent or long-term antibiotic use can alter the gut microbiome, resulting in fungal overgrowth.
Eating a diet high in carbohydrates and processed foods may also cause gastrointestinal problems. Research shows that people with auto-brewery syndrome often report eating a “high sugar, high carbohydrate diet.”
Auto-brewery syndrome is a rare condition that the medical community first reported on in the 1950s.
Since its initial discovery, researchers have diagnosed auto-brewery syndrome in both adults and children.
However, the authors of a 2019 case report in BMJ Open Gastroenterologybelieve that auto-brewery syndrome may be an underdiagnosed medical condition.
The early symptoms of auto-brewery syndrome include:
- brain fog
- slurred speech
- mood changes
Auto-brewery syndrome can also cause other symptoms, such as:
- loss of coordination
- memory problems
- difficulty concentrating
A doctor can diagnose auto-brewery syndrome using a combination of laboratory and observational tests.
It is a rare condition, so a person will usually undergo testing for more common illnesses first.
Doctors typically begin the diagnostic process by reviewing a person’s medical history, asking about their current symptoms, and performing a physical examination.
A doctor may recommend additional tests if they suspect that the person’s symptoms are due to auto-brewery syndrome or another gastrointestinal disease.
The doctor may collect a small stool sample, which they will send to a laboratory for analysis. This analysis usually involves checking for abnormal concentrations of bacteria and fungi.
Doctors can also use a long, thin tube called an endoscope to collect fluid from different parts of the gastrointestinal tract. These samples will go to a laboratory, where people will look for bacterial or fungal overgrowth.
Some doctors may use a carbohydrate challenge test to test for auto-brewery syndrome. They will ask the individual to eat a carbohydrate-rich meal or take a glucose (sugar) capsule on an empty stomach.
After a few hours, they will check the person’s blood alcohol level. People who do not have auto-brewery syndrome have almost undetectable blood alcohol levels. An increase in blood alcohol levels after the carbohydrate challenge test may, therefore, indicate auto-brewery syndrome.
Doctors may run additional tests on a person’s blood and urine to rule out any possible underlying conditions that could explain their symptoms.
There are several different treatment options for auto-brewery syndrome, including:
Avoiding carbohydrates and processed foods can help relieve some symptoms of auto-brewery syndrome.
People who choose to restrict their carbohydrate intake can try eating more protein to help them feel fuller for longer.
People who have auto-brewery syndrome should avoid simple carbohydrates and refined foods with added sugars, such as:
- white bread
- white rice
- pastries and desserts
- high fructose corn syrup
- sugars, including glucose, fructose, and dextrose
- sugary beverages, such as soda and fruit juice
A doctor will likely recommend that people follow a low sugar diet until their symptoms resolve. People who no longer experience symptoms can try gradually reintroducing carbohydrates to their diet.
People should speak with their doctor before making any dietary changes that might affect their treatment plan.
Doctors can treat auto-brewery syndrome with antifungals and, in some cases, antibiotics. Antifungals can help reduce the amount of fungus in the gut.
Doctors also use these drugs to treat fungal infections that cause gastrointestinal symptoms.
Antifungal drugs that people may take to treat auto-brewery syndrome include:
- fluconazole (Diflucan)
- itraconazole (Sporanox)
- nystatin (Mycostatin)
- echinocandins, such as caspofungin (Cancidas)
People who do not respond to first-line treatment may require stronger medication.
Probiotic supplements may help balance the microbiota in the gut by introducing beneficial bacteria and inhibiting fungal growth.
However, the exact role of probiotic supplementation as a treatment for auto-brewery syndrome remains unclear.
Many people resume their regular diet and lifestyle after one treatment. However, some people experience recurring symptoms even after being asymptomatic.
Other ways of managing auto-brewery syndrome include:
- treating any underlying medical conditions
- losing weight, if necessary
- limiting or avoiding foods and drinks that contain added sugar
- choosing complex carbohydrates over simple carbohydrates
Although auto-brewery syndrome is a rare condition, a few reported cases have made news headlines.
In 2015, the BBC published a story about a man who claimed to experience symptoms of drunkenness after eating carbohydrates. When he told his friends that he had not consumed alcohol, they assumed that he was lying.
The BBC explain:
At first, [he] didn’t really know what was happening. “It was weird, I’d eat some carbs, and all of a sudden, I was goofy, vulgar.”
He would get inexplicably sick, with stomach pains and headaches. “Every day for a year, I would wake up and vomit,” he says. “Sometimes, it would come on over the course of a few days, sometimes, it was just like, ‘Bam! I’m drunk.’”
According to CNN, the judge dropped the DUI charges “after being presented with evidence the woman suffers from ‘auto-brewery syndrome.’”
A 2013 case study on a 61-year-old man found that an overgrowth of the fungus Saccharomyces cerevisiae — the same fungus as brewer’s yeast — was causing auto-brewery syndrome.
After using antifungals and changing to a low carbohydrate diet, the man’s symptoms resolved.
Auto-brewery syndrome is a rare condition that occurs when yeast in the gut produces excessive quantities of ethanol, which can cause symptoms similar to those of being drunk.
People who have auto-brewery syndrome register abnormally high blood alcohol levels, even if they consume no alcohol.
Antifungal medications and eating a diet low in sugar and carbohydrates can help minimize the effects. People should speak to a doctor if they think that they are experiencing symptoms of auto-brewery syndrome.